Electric energy storage apparatus

1. An electric energy storage apparatus configured to receive and store at least one of first electric energy supplied from a grid or second electric energy supplied from a generator, and supply the stored electric energy or electric energy supplied from at least one of the grid and the generator to an electric load, wherein the electric load comprises a (1) first load being an ordinary load that receives electric energy supplied from the grid and consumes the received electric energy, and (2) a second load that receives energy supplied from the grid or energy supplied by the discharge of a battery and consumes the received energy, and the second load is a critical load being an electric load selectively designated by a user, and wherein the electric energy storage apparatus is configured to sense a magnitude of electric energy flowed out to the grid in an operation mode of supplying the stored electric energy to the electric load, and selectively block the output of the stored electric energy when the sensed magnitude of electric energy exceeds a preset first threshold value, the electric energy storage apparatus comprising: a battery configured to store electric energy supplied from any one of the grid and the generator, and selectively output the stored electric energy; a first switch disposed between a connection node connecting the grid to the generator and the battery; a second switch disposed between the battery and the second load; a third switch disposed between the grid and the second load that opens or closes a supply path of electric energy supplied from the grid to the second load; a first sensing unit disposed between the grid and the third switch to sense an electric energy state at the disposed position; a controller configured to sense whether or not electric energy flows out to the grid through the first sensing unit in a state that the third switch is off, and selectively stop a discharge operation of the battery according to the sensing result; a fourth switch disposed between the grid and the second load and connected in series to the third switch that opens or closes an electric energy flow path between the grid and the second load; and a second sensing unit disposed between the third switch and the fourth switch, wherein the fourth switch replaces the third switch and performs an operation of the third switch in a state in which the third switch is not normally operated.

2. The electric energy storage apparatus of claim 1 , wherein an operation mode of the electric energy storage apparatus comprises at least one of: a first operation mode for charging the battery using the first electric energy, a second operation mode for charging the battery using the second electric energy, a third operation mode for supplying the first electric energy to the second load and charging the second electric energy to the battery, a fourth operation mode for supplying the first electric energy to the second load, and a fifth operation mode for supplying electric energy stored in the battery to the second load.

3. The electric energy storage apparatus of claim 2 , wherein the controller is configured to sense the presence of electric energy flowed out to the grid based on a magnitude of electric energy sensed through the first sensing unit in the fifth operation mode.

4. The electric energy storage apparatus of claim 2 , wherein the controller is configured to sense the presence of electric energy flowed out to the grid based on a state of electric energy sensed through the second sensing unit.

5. The electric energy storage apparatus of claim 3 , wherein when a magnitude of electric energy sensed through the second sensing unit increases to more than a preset second threshold value, the controller is configured to determine that the electric energy flows out to the grid and to stop the supply of electric energy from the battery to the second load.

6. The electric energy storage apparatus of claim 1 , wherein the controller is configured to change a switching state of the auxiliary switch when a magnitude of electric energy sensed through the first sensing unit exceeds the first threshold value.

7. The electric energy storage apparatus of claim 1 , wherein the auxiliary switch is configured to maintain an on-state in the first to fifth operation modes, and to be changed to an off-state as the magnitude of the electric energy exceeds the first threshold value.

8. The electric energy storage apparatus of claim 7 , further comprising: a third sensing unit disposed between the grid and the auxiliary switch, wherein the controller is configured to stop the supply of electric energy to the second load when a magnitude of electric energy sensed through the third sensing unit exceeds the first threshold value.